1. Field of the Invention
The present invention relates to a lens apparatus that performs a wobbling motion of a focus lens in order to determine a driving direction of the focus lens in which an object image comes closer to an in-focus state, and also relates to an imaging apparatus including the same.
2. Description of the Related Art
In a conventional still image capturing imaging apparatus or a conventional moving image capturing imaging apparatus, in order to determine a driving direction of a focus lens in which an object image formed by an imaging optical system comes to be in focus, the focus lens is minutely moved back and forth (i.e., a wobbling motion) in an optical axis direction of the imaging optical system.
For example, as discussed in Japanese Patent Application Laid-Open No. 2010-63162, the wobbling motion of a focus lens is performed in a plurality of follow-up modes independent from a frequency of an exposure synchronization while taking the exposure synchronization between a camera apparatus and a lens apparatus. Discussed therein is that the focus lens can be controlled at an appropriate frequency for the wobbling motion of the focus lens.
However, in the conventional art discussed in the above-described Japanese Patent Application Laid-Open No. 2010-63162, each follow-up mode has only one driving frequency (i.e., driving speed) during the wobbling motion. Further, as a mechanism design for causing the focus lens to operate in an optical axis direction, it is difficult to eliminate a back-lash of a connection unit in view of operation guarantee and part accuracy under various temperatures. As a result thereof, a mechanical collision noise cannot be prevented from being generated during the wobbling motion.
Therefore, in a case where the driving frequency is increased in order to improve controllability, the mechanical collision noise increases and thus such an inconvenience occurs that the noise tends to be recorded by a camera microphone as an operation noise of the focus lens. In the wobbling motion, an automatic focus operation is realized by causing the focus lens to move back and forth in an optical axis direction at a minute drive amplitude value to the extent that humans cannot visually confirm it in an captured moving image and a through-image.
The mechanical collision noise generated during the wobbling motion is a periodic sound generated in a short period such as an imaging period (i.e., a frame rate), so that the noise tends to be recognized as a grating sound in an audibility of human. Therefore, when capturing a moving image, recording of the mechanical collision noise generated during the wobbling motion is recognized as an unpleasant sound for a viewer of the moving image, resulting in inviting degradation of video quality (including sound).
A conventional camera has a through-image display function for causing a liquid crystal display provided on the rear surface of a camera body to display an image captured by an image sensor. The through-image is an image which is not to be recorded on a recording medium, such as a memory card, after the image capturing. An operator visually confirms the through-image, thereby being able to determine the composition of an object when capturing a still image thereof.
The mechanical collision noise generated during the wobbling motion does not involve a change of the captured moving image or through-image, so that the noise tends to be recognized as the grating sound in the audibility of human. Therefore, when capturing a moving image, recording of the mechanical collision noise during the wobbling motion and generation of the mechanical collision noise when capturing a still image or a moving mage are recognized as the unpleasant sound for the operator and a viewer of the moving image, resulting in inviting the degradation of the video quality (including sound).